JP2008045591A - Hydraulic auto-tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic auto-tensioner having a compact axial length. <P>SOLUTION: A sleeve 13 is incorporated in a cylinder 11, and a flange 14 provided at the lower end of the sleeve 13 is supported by a stepped portion 15 provided at the inner periphery lower part of the cylinder 11. A rod 16 is inserted into the cylinder 11 to be partitioned into a pressure chamber 17 and a reservoir chamber 18. A spring seat 20 is mounted at the upper end of the rod 16, and a return spring 21 is incorporated between the spring seat 20 and the flange 14 for energizing the rod 16 to the direction of increasing the capacity of the pressure chamber 17. A passage 27 is formed in the flange 14 between the pressure chamber 17 and the reservoir chamber 18. The passage 27 is opened and closed by a check valve 30. This results in a compact axial length. A cylinder 22 is provided for covering the upper outer periphery of the cylinder 11, and an oil seal 24 is mounted in a seal groove 23 formed at the upper part outer periphery of the cylinder 11. The oil seal 24 is put in elastic contact with the inner periphery of the cylinder 22. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hydraulic auto tensioner used for maintaining tension of a belt for driving an automobile auxiliary machine such as an alternator, a water pump, and an air conditioner compressor.

  In a belt transmission that transmits the rotation of the crankshaft of an engine to various automotive accessories, a swingable pulley arm that supports a tension pulley is provided on the slack side of the accessory driving belt, and a hydraulic auto tensioner is installed on the pulley arm. An adjustment force is applied to urge the pulley arm in a direction in which the tension pulley presses the belt, so that the belt tension is kept constant.

  As a hydraulic auto tensioner used in the belt transmission device as described above, those described in Patent Document 1 and Patent Document 2 are conventionally known. In this hydraulic auto tensioner, an oil seal that prevents leakage of hydraulic oil filled in the cylinder is incorporated in the upper opening of the cylinder in which the sleeve is built, and slidably penetrates the oil seal. A spring seat is provided at the upper end of the rod, and a return spring is built in between the spring seat and the flange provided at the lower outer periphery of the cylinder to give the rod an outward projecting force. The force is buffered by a hydraulic damper provided inside the sleeve.

  Here, the hydraulic damper is provided with a plunger slidable in the sleeve at the lower end portion of the rod, the inside of the cylinder is partitioned into a pressure chamber and a reservoir chamber, and a passage that communicates the pressure chamber and the reservoir chamber with the plunger is provided. The check valve is provided in the opening on the pressure chamber side of the passage, and when the rod is pushed and the pressure in the pressure chamber becomes higher than the pressure in the reservoir chamber, the passage is closed by the check valve and the hydraulic oil in the pressure chamber closes the rod. The pushing force applied to the is buffered.

JP-A-10-19099 JP-A-10-306860

  By the way, in the conventional hydraulic auto tensioner, a passage communicating the pressure chamber and the reservoir chamber is formed in the plunger provided at the lower portion of the rod, and the passage is opened and closed by the check valve. The length was long, and it was necessary to secure a large space for the assembly of the hydraulic auto tensioner, and there were points to be improved in order to make the axial length compact.

  An object of the present invention is to provide a compact hydraulic auto tensioner having an axial length which can prevent leakage of hydraulic oil to the outside.

  In order to solve the above problems, in the present invention, a sleeve is incorporated into a bottomed cylinder filled with hydraulic oil, and the outer peripheral portion of the lower surface of the outward flange formed at the lower end of the sleeve is provided. The cylinder is supported by a step provided at the lower inner periphery of the cylinder, the lower end of the rod is slidably inserted into the sleeve, and the cylinder is partitioned into a pressure chamber and a reservoir chamber, and the cylinder of the rod A spring seat having a cylindrical portion covering the upper outer periphery of the cylinder is attached to the upper end portion located outside from the upper opening of the cylinder, and a return spring is assembled between the spring seat and the flange of the sleeve, and formed below the flange. The rod is urged in the direction of increasing the volume of the pressure chamber, a seal groove is formed on the outer periphery of the cylinder, and an oil seal incorporated in the seal groove is elastically contacted with the inner periphery of the cylindrical portion. The flange is sealed between the fitting surface of the cylinder and the cylinder, and the flange is provided with a passage communicating with the pressure chamber and the reservoir chamber provided above the flange, and the pressure chamber has an opening on the pressure chamber side. A configuration is adopted in which a check valve is provided for closing the passage when the pressure in the chamber becomes higher than the pressure in the reservoir chamber.

  As described above, a flange is provided at the lower end portion of the sleeve into which the lower end portion of the rod is slidably inserted, and a passage that connects the pressure chamber and the reservoir chamber is formed in the flange, and the passage is opened and closed by the check valve. As a result, the axial length can be reduced compared to a hydraulic auto tensioner in which a passage is formed in a plunger provided at the lower portion of the rod and the passage is opened and closed by a check valve.

  In addition, by installing an oil seal in the seal groove formed on the outer periphery of the cylinder and sealing between the cylinder and the cylindrical part of the spring seat, leakage of hydraulic oil filled in the cylinder to the outside is prevented. In addition, foreign matter can be prevented from entering the cylinder from the outside.

  Furthermore, by sealing between the cylinder and the cylindrical portion with an oil seal, it is possible to freely design the number of lips, the lip shape, and the tightening force to be brought into elastic contact with the inner periphery of the cylindrical portion.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a belt tension adjusting device. As shown in the figure, the pulley arm 1 is supported so as to be swingable about a fulcrum shaft 2, and a tension pulley 4 that applies tension to the belt 3 is rotatably supported at the end of the swing side.

  Further, a hydraulic auto tensioner 10 according to the present invention is connected to the pulley arm 1, and the pulley arm 1 is urged by the hydraulic auto tensioner 10 in a direction in which the tension pulley 4 presses the belt 3.

  As shown in FIG. 2, the hydraulic auto tensioner 10 has a bottomed cylindrical cylinder 11 whose upper end is open, and the cylinder 11 is filled with hydraulic oil. A connecting piece 12 connected to the engine block A is provided on the lower surface of the cylinder 11.

  A sleeve 13 is incorporated in the cylinder 11. The sleeve 13 has an outward flange 14 at the lower end, and the outer periphery of the lower surface of the flange 14 is supported by a step portion 15 provided at the lower inner periphery of the cylinder 11.

  In forming the step portion 15, here, the bottomed cylindrical body B is fitted into the cylinder 11, and the upper end of the cylindrical body B is used as the step portion 15, but a small-diameter concave portion is formed at the bottom portion of the cylinder 11. Alternatively, a stepped portion may be provided directly on the lower inner periphery of the cylinder 11.

  A lower end portion of a rod 16 is slidably inserted into the sleeve 13, and the inside of the cylinder 11 is partitioned into a pressure chamber 17 and a reservoir chamber 18 by the rod 16 and the sleeve 13.

  A connecting piece 19 connected to the pulley arm 1 is connected to an upper end portion of the rod 16 that is located outside the upper end opening of the cylinder 11. A spring seat 20 is fixed to the lower end of the connecting piece 19 at the upper end of the rod 16, and a return spring 21 is incorporated between the spring seat 20 and the flange 14 of the sleeve 13. The return spring 21 urges the rod 16 in the direction in which the volume of the pressure chamber 17 provided below the flange 14 increases.

  The spring seat 20 has a cylindrical portion 22 covering the upper outer periphery of the cylinder 11 on the outer periphery. On the other hand, an annular seal groove 23 is formed on the upper outer periphery of the cylinder 11, and an oil seal 24 is incorporated in the seal groove 23.

  As shown in FIG. 6, the oil seal 24 has a plurality of lips 24a, 24b on the outer periphery, and each lip 24a, 24b is in elastic contact with the inner periphery of the cylindrical portion 22 as shown in FIG. 11 and the fitting surface of the cylindrical portion 22 are sealed to prevent the hydraulic oil in the reservoir chamber 18 from leaking to the outside.

  Further, an annular protrusion 25 is formed on the lower outer periphery of the seal groove 23 on the upper outer periphery of the cylinder 11. On the other hand, a retaining claw 26 is provided on the inner peripheral lower portion of the cylindrical part 22. The abutment of the retaining claw 26 against the rod 16 prevents the rod 16 from coming out of the cylinder 11.

  As shown in FIGS. 3 and 4, a plurality of arc-shaped passages 27 communicating with the pressure chamber 17 and the reservoir chamber 18 are formed on the same circle in the flange 14 of the sleeve 13. A check valve 30 that closes the passage 27 when the pressure in the pressure chamber 17 becomes higher than the pressure in the reservoir chamber 18 is provided in the opening on the side.

  The check valve 30 has a lower surface of the flange 14 as a seat surface 31, and a ring-shaped valve body 32 having a square cross section is provided in contact with and separated from the seat surface 31. The valve body 32 is seated by a valve spring 33. When the pressure in the pressure chamber 17 becomes higher than the pressure in the reservoir chamber 18 by urging toward the surface 31, the valve body 32 is brought into contact with the seat surface 31 to close the passage 27.

  Here, as the valve spring 33, a press-formed product of a thin metal plate in which a plurality of inward elastic pieces 33b are formed at equal intervals in the circumferential direction at the lower end edge of the annular portion 33a press-fitted into the inner periphery of the pressure chamber 17 The valve body 32 is urged toward the seat surface 31 by the elastic piece 33b, but a disc spring or a coil spring may be used.

  The belt tension adjusting device shown in the embodiment has the above-described structure, and the tension of the belt 3 changes due to the load fluctuation of the auxiliary machine driven by the belt 3 and the change of the angular velocity of the crankshaft, and the belt 3 is slack. When it occurs, the rod 16 moves outward by the pressing of the return spring 21 and absorbs the slack of the belt 3.

  At this time, when the volume of the pressure chamber 17 is increased and the pressure is decreased and the pressure is lower than the pressure of the reservoir chamber 18, the valve body 32 of the check valve 30 is separated from the seat surface 31 as shown in FIG. In order to open the passage 27, the hydraulic oil in the reservoir chamber 18 flows from the passage 27 to the pressure chamber 17, and the rod 16 rapidly moves outward to absorb the slack of the belt 3 immediately.

  On the other hand, when the tension of the belt 3 increases, a pushing force is applied from the belt 3 to the rod 16. At this time, since the pressure in the pressure chamber 17 becomes higher than the pressure in the reservoir chamber 18, the valve body 32 of the check valve 30 contacts the seat surface 31 to close the passage 27, and the hydraulic oil sealed in the pressure chamber 17 The pushing force applied to the rod 16 is buffered.

  When the pushing force is larger than the elastic force of the return spring 21, the hydraulic oil in the pressure chamber 17 flows into the reservoir chamber 18 through a minute leak gap b formed between the sliding surfaces of the sleeve 13 and the rod 16, and the pushing force The rod 16 is slowly retracted to a position where the elastic force of the return spring 21 is balanced, and the tension of the belt 3 is kept constant.

  As shown in the embodiment, a flange 14 is provided at the lower end of the sleeve 13 into which the lower end of the rod 16 is slidably inserted, and a passage 27 for communicating the pressure chamber 17 and the reservoir chamber 18 is formed in the flange 14. Then, by opening and closing the passage 27 with the check valve 30, the plunger of the hydraulic auto tensioner shown in Patent Document 1 and Patent Document 2 described above can be omitted, and the axial direction of the hydraulic auto tensioner correspondingly. The length can be made compact.

  In addition, an oil seal 24 is attached to a seal groove 23 formed in the upper peripheral portion of the cylinder 11 and the space between the cylinder 11 and the cylindrical portion 22 of the spring seat 20 is sealed, so that the outside of the hydraulic oil filled in the cylinder 11 is removed. Can be prevented, and foreign matter can be prevented from entering the cylinder 11 from the outside.

  Further, by sealing between the cylinder 11 and the cylindrical portion 22 with the oil seal 24, the number of lips 24a and 24b to be brought into elastic contact with the inner periphery of the cylindrical portion 22, the lip shape, and the tension force can be freely designed.

Front view showing a belt tension adjusting device using a hydraulic auto tensioner according to the present invention. Sectional view along the line II-II in FIG. Enlarged cross-sectional view of the check valve section of the hydraulic auto tensioner shown in FIG. Sectional view along line IV-IV in FIG. Sectional view showing the open state of the check valve Sectional view showing the natural state of the oil seal installed in the seal groove

Explanation of symbols

11 Cylinder 13 Sleeve 14 Flange 15 Step 16 Rod 17 Pressure chamber 18 Reservoir chamber 21 Return spring 22 Cylindrical portion 23 Seal groove 24 Oil seal 27 Passage 30 Check valve

Claims (1)

  A sleeve is built into a bottomed cylinder filled with hydraulic oil inside, and the outer periphery of the lower surface of the outward flange formed at the lower end of the sleeve is supported by a step provided at the lower inner periphery of the cylinder. The lower end portion of the rod is slidably inserted into the sleeve, the inside of the cylinder is partitioned into a pressure chamber and a reservoir chamber, and the upper portion of the cylinder is located at the upper end portion of the rod located outside the upper opening of the cylinder. A spring seat having a cylindrical portion covering the outer periphery is attached, and a return spring is incorporated between the spring seat and the flange of the sleeve to urge the rod in a direction in which the volume of the pressure chamber formed below the flange increases. And forming a seal groove on the outer periphery of the cylinder, and an oil seal incorporated in the seal groove is brought into elastic contact with the inner periphery of the cylindrical portion to seal between the fitting surface of the cylindrical portion and the cylinder, A check valve that closes the passage when the pressure in the pressure chamber becomes higher than the pressure in the reservoir chamber is provided in the lunge in a passage that communicates the pressure chamber and the reservoir chamber provided above the flange. Hydraulic auto tensioner with

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